On 11/30/22 00:34, Huang, Kai wrote: > On Wed, 2022-11-30 at 11:35 +0800, Binbin Wu wrote: >> On 11/21/2022 8:26 AM, Kai Huang wrote: >>> After the array of TDMRs and the global KeyID are configured to the TDX >>> module, use TDH.SYS.KEY.CONFIG to configure the key of the global KeyID >>> on all packages. >>> >>> TDH.SYS.KEY.CONFIG must be done on one (any) cpu for each package. And >>> it cannot run concurrently on different CPUs. Implement a helper to >>> run SEAMCALL on one cpu for each package one by one, and use it to >>> configure the global KeyID on all packages. >>> >>> Intel hardware doesn't guarantee cache coherency across different >>> KeyIDs. The kernel needs to flush PAMT's dirty cachelines (associated >>> with KeyID 0) before the TDX module uses the global KeyID to access the >>> PAMT. Following the TDX module specification, flush cache before >>> configuring the global KeyID on all packages. >>> >>> Given the PAMT size can be large (~1/256th of system RAM), just use >>> WBINVD on all CPUs to flush. >>> >>> Note if any TDH.SYS.KEY.CONFIG fails, the TDX module may already have >>> used the global KeyID to write any PAMT. Therefore, need to use WBINVD >>> to flush cache before freeing the PAMTs back to the kernel. Note using >>> MOVDIR64B (which changes the page's associated KeyID from the old TDX >>> private KeyID back to KeyID 0, which is used by the kernel) >> >> It seems not accurate to say MOVDIR64B changes the page's associated KeyID. >> It just uses the current KeyID for memory operations. > > The "write" to the memory changes the page's associated KeyID to the KeyID that > does the "write". A more accurate expression perhaps should be MOVDIR64B + > MFENSE, but I think it doesn't matter in changelog. Just delete it from the changelog. It's a distraction. I'm not even sure it's *necessary* to do any memory content conversion after the TDX module has written gunk. There won't be any integrity issues because integrity errors don't do anything for KeyID-0 (no #MC). I _think_ the reads of the page using KeyID-0 will see abort page semantics. That's *FINE*.
